Home porting, exhaust crush gasket???

Bill Hilly · 01-08-2024, 11:14 AM

I am porting my head while waiting for parts, and while portion the exhaust, I notice that the crushed gasket has a thin ring pushed up , kinda forming a thin lip. . I assume that the new gasket will do the same, SO, should I stop enlarging the opening?, or grind through the ring? Thanks. This is a poor picture, but it shows the ring in the gasket.http://

Thumper · 01-08-2024, 11:32 AM

Good plan!

I think the seal will still be made since the crushable gasket should fit around the circumference tightly, and the exhaust should still crush the entire gasket. You might remove that old one and see how the replacement crushable gasket fits.

The broad seat that has a visible exposed surface inside the crushed gasket can be ground down as long as the new gasket still fits on the flat surface in the circumference. I think that port near the gasket is not ground out as far as it could be. The gasket will crush inward slightly, so leave a little flat surface for it.

Looking into the port, those surfaces deeper into the port are more important, but even a slight grind to enlarge the exhaust port near the gasket can't hurt, as long as the replacement gasket has flat surface to be crushed on.

You can use the replacment gasket as a measuring device periodically while you make progress on the grind.

XLsior · 01-08-2024, 04:38 PM

most of the restricting is around the valve seat and and opposed throat ceiling, The actual exit diameter isn't the main restriction point and opening to much could lead into a mating surface lip issue between the crush gasket and header pipe...which would be worse....

JohnC · 01-08-2024, 04:47 PM

Here are some gaskets I used after porting the head on my Brozz 250. I did have to kinda pry the old seal out. The original gasket was not usable and certainly was not going to seal.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

John

01-08-2024, 11:14 AM	#1
Bill Hilly Join Date: Feb 2021 Posts: 934	Home porting, exhaust crush gasket??? I am porting my head while waiting for parts, and while portion the exhaust, I notice that the crushed gasket has a thin ring pushed up , kinda forming a thin lip. . I assume that the new gasket will do the same, SO, should I stop enlarging the opening?, or grind through the ring? Thanks. This is a poor picture, but it shows the ring in the gasket.http://
	1

01-08-2024, 11:32 AM	#2
Thumper Join Date: Feb 2021 Location: Kansas City Posts: 2,310	Good plan! I think the seal will still be made since the crushable gasket should fit around the circumference tightly, and the exhaust should still crush the entire gasket. You might remove that old one and see how the replacement crushable gasket fits. The broad seat that has a visible exposed surface inside the crushed gasket can be ground down as long as the new gasket still fits on the flat surface in the circumference. I think that port near the gasket is not ground out as far as it could be. The gasket will crush inward slightly, so leave a little flat surface for it. Looking into the port, those surfaces deeper into the port are more important, but even a slight grind to enlarge the exhaust port near the gasket can't hurt, as long as the replacement gasket has flat surface to be crushed on. You can use the replacment gasket as a measuring device periodically while you make progress on the grind. __________________ -2022 5 speed Templar X Orange, OEM 51T rear sprocket, 14T front sprocket -NOS 2020 KTM 250SX (2-stroke motocross), less than 10 hours on it
	2

01-08-2024, 04:38 PM	#3
XLsior Join Date: Aug 2020 Location: Australia Posts: 1,289	most of the restricting is around the valve seat and and opposed throat ceiling, The actual exit diameter isn't the main restriction point and opening to much could lead into a mating surface lip issue between the crush gasket and header pipe...which would be worse....
	0

01-08-2024, 04:47 PM	#4
JohnC Join Date: Oct 2020 Location: Southeast Michigan Posts: 99	Here are some gaskets I used after porting the head on my Brozz 250. I did have to kinda pry the old seal out. The original gasket was not usable and certainly was not going to seal. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 John
	0